A major goal of the coming year will be to compare the rate of recovery of brain acetycholinesterase (AChE) activity with the recovery of blood AChE activity and the appearance of blood and urine metabolites of parathion with time after a single administration of parathion in the monkey. At the present time no information exists on the correlation of recovery of blood and brain AChE activity because of the prohibitive cost of the monkeys required for such a study. However, a method of serial collection of cores of cortical samples before and after parathion administration will be used so that each animal will be his own control and the animal need not be sacrificed to determine the effects on brain AChE activity. Other goals for the coming year will be to determine the effects of subacute administration of parathion in rats and monkeys on such indices of nervous system function as brain electrical activity in both rats and monkeys and on performance of a learned task in monkeys.